Qmake: Move Qt library path after other libraries

Paths are prepended, so the first one to be added is actually the last
search path.

On a debian machine with system-installed Qt and Qbs, if you execute Qtc
from another instance of Qtc with "Add build library search path" checked,
LD_LIBRARY_PATH has /usr/lib/x86_64-linux-gnu before $BUILD/lib/qtcreator.

This means that the system's Qbs lib will be loaded instead of the one in
RPATH, which is bad (i.e. qbs build fails because it cannot find
$BUILD/lib/x86_64-linux-gnu/qbs/qbs_processlauncher).

Change-Id: Ibe6778ba8a06da1680e034e31a8fee6d9a81c484
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/libs/utils/environment.h

@@ -101,6 +101,7 @@ public:
     void prependOrSetPath(const QString &value);
 
     void prependOrSetLibrarySearchPath(const QString &value);
+    void prependOrSetLibrarySearchPaths(const QStringList &values);
 
     void clear();
     int size() const;